Preparation of hydrosilanes

ABSTRACT

Hydrosilanes are produced by contacting a disilane with hydrogen gas under pressure and thereafter heating the mixture in the presence of a transition metal catalyst such as palladium on charcoal. The recovered hydrosilanes are particularly useful as precursors in the production of other useful materials.

United States Patent Atwell et al.

[ Feb. 1, R972 [54] PREPARATION OF HYDROSILANES [72] Inventors: William H. Atwell; Rudolf M. Salinger;

Richard P. Seibert, all of Midland, Mich.

[731 Assignee: Dow Corning Corporation, Midland, Mich.

[22] Filed: Mar. 27, 1970 [21] Appl. No.: 23,443

lnouye, Chemical Abstracts, (1959), Vol. 53, pages 17,888- 17,889 QDIAS 1.

Primary Examiner-James E. Poer Assistant Examiner-Werten F. W. Bellamy Attorney-Robert F. Fleming, Jr., Laurence R. Hobey, Harry D. Dingman, Howard W. Hermann and Joseph R. Radzius [57] ABSTRACT Hydrosilanes are produced by contacting a disilane with hydrogen gas under pressure and thereafter heating the mixture in the presence of a transition metal catalyst such as palladium on charcoal. The recovered hydrosilanes are particularly useful as precursors in the production of other useful materials.

10 Claims, No Drawings PREPARATION OF HYDROSILANES This invention relates to a process for preparing hydrosilanes of the formula R SiH, comprising A. contacting course, that in certain cases the disilane (I) may consist of mixture of materials. For example, when the disilane (l contains both alkyl and halogen substituents in combination such as dimethyl-tetrachlorodisilane and its isomers, trimethyll. a disilane of the formula R Si-SiR in which R is 5 trichlorodisilane and its isomers, tetramethyldichlorodisilane selected from the group consisting of alkyl radicals of and its isomers, and pentamethylchlorodisilane, these materifrom one to six carbon atoms carbon atoms inclusive, als may be obtained from the high boiling residue formed alkoxy radicals of from one to six carbon atoms incluwhen methyl chloride is passed over silicon in the presence of sive, a phenyl radical, a halogen atom, a 3,3,3- heat and a copper catalyst. If desired, the illustrative aforetrifluoropropyl radical, a hydrogen atom, and a mentioned mixture may be separated and its individual comtrimethylsiloxy radical, with ponents may be employed in the process described herein, or

2. hydrogen gas under pressure, and the mixture itself may be used.

B. heating the above admixture at a temperature of from 25 The method de ribed herein mu t be conducted under C. to 250C.,in the presence of pressure which may vary from 50 p.s.i.g. to 3,000 p.s.i.g. or

3. at least 1.0 percent by weight based upon the weight of more. Absent the necessary pressure, the reaction will not the disilane (l) of a transition metal catalyst, and proceed or will proceed so slowly as to be economically imthereafter practical. Selection of the most effective pressure is also derecovering the hydrosilahependent upon the specific structure of the disilane l For ex- AS "Qted above, R can be an alkyl radical of from one to 51X ample, halogen-substituted disilanes tend to require more carbon atoms Such as the y y P PYL P PYL pressure, e.g., about 1,000 or more p.s.i.g., than do alkyl-sub- W yh y and the heXyl l'adleal- R y also be an stituted disilanes which require as little as 50 p.s.i.g. k y radical of m n to six carbon atoms such as h The method described herein may be readily conducted at methexy, yi P P Y yi the heXOXY radicalin essentially room temperature or C. However, to facilitate addition, R can be a p y radical, a hydrogen atom, a lthe reaction it is preferred that a moderate temperature of lrifluowpwpyl radical. a trimethylsiloxy H m J radical. from about 100 c. to about 150 c. be employed. At tcmor f h g atom Such as the Chlorine elem bromine atom, peratures in excess of 250 C., catalyst and/or disilane decomledme atom position tends to occur which deleteri-ously affects the rcac The term transition metal catalyst is understood to mean tion. and is intended to include materials such as palladium on The ingredients l (2), and (3) may be mixed in any concharcoal, ruthenium on charcoal, rhodium on charcoal and ventional manner and in any order most feasible and conthe like. The aforementioned transition metal catalysts" are venient under the circumstances. The best means of practicing commercially available materials which are well known in the th present invention, how v is to ix the disilane 1 with FOF pl these are normally provided in powdered or the desired catalyst (3), The mixture is then contacted with pellet form and consist of the metal, e.g., palladium at 5 perthe hydrogen gas under the appropriate pressure. The cent or greater on a charcoal support. Charcoal supports conhydrosilane is then recovered in standard fashion. taining 5 percent or more metal have been found to be suita- In contrast the methods known in the art, under the condible for purposes of the present invention; however, in view of {ions d by h th d d ib d he i significantly in- BCOnOrniCal Considerations and the like, a pp Containing creased yields of the hydrosilanes are obtained. In addition, from about 5 to about 15 P r nt me l i parti l rly Suitaheretofore, it was not possible to cleave the silicon-silicon l M v l V, WWW MMMW w "Wm linkage by means of hydrogenolysis under such mild condi- The term transition metal catalysts" is also intended to entiOnS, at temperatures of 1e55- compass materials which are not commercially available such The hydro i es hi are in r useful 88 P F as a variety of organophosphine complexes of transition sors in the production of other useful materials, e.g., metals, e.g., [(organo) Pi PdCl [(organo) P] PtCl-,,, [(orhydrogen-substituted siloxanes which in themselves are useful gano), PJ NiCI and the like in which the organo group is as crosslinkers for silicone elastomers. The hydrosilanes are representative of a phenyl radical or an alkyl radical of from also employed for the preparation oforgano functional derivaone to six carbon atoms (illustrative examples of which have tives by addition to suitable olefin compounds. been noted above). These organophosphine complexes of The following example is illustrative only and is not intransition metals are prepared by merely adding the ortended to limit the invention which is properly delineated in ganophosphine, e.g., tributyl phosphine, to either an aqueous the appended claims. or alcoholic solution of the appropriate transition metal salt, e.g., x,Pdc|,. y EXAMPLE 1 The particular transition metal catalyst which is most effec- The disilane, catalyst, and a solvent* were added to a suitative is dependent upon the specific structure of the disilane ble hydrogenation apparatus. The desired hydrogen gas pres- That is, it has been found that when the disilane sure was applied followed by the proper application of heat. thins y alkyl g p Such as y the aforementioned Subsequent to reaction, the reaction product was analyzed by commercially available catalysts such as palladium on chargas Chromatography and in all Cases, the products wcrc coal function best, whereas when the disilane (1) contains a id tifi d by the use f known Standards halogen atom such as chlorine, the aforementioned organo- F l pressure runs i, t d rd P Phosphihe complexes Oftransitioh i -g-i [(H"C4HQ)3P] hydrogenation apparatus was employed. The high pressure a a TFP PQi UYHlE bE v runs 100 p.s.i.g.) were carried out in a pressure reactor The disilanes (l) are readily available and well-known equipped with a gas boost compressor and magnetically driven materials. That is, the disilane (1) can be prepared by stanstirrer. The results obtained (using a variety of disilanes and dard means, e.g., alkoxylation, the Grignard process, and catalysts) under the prescribed conditions are provided in the reduction of alkylchlorodisjlanes. is to be understood, of following Tablel.

TABLE I Pressure Catalyst: type (g.) Disilane (g.) (p.s.i.g.) Temp. C.)

57 Pd G (10) (Clinton-sinus) 2 1, 520 150 5% Pt 0 (8.9) (crouch-sh (111) 4,100 250 5% Ru/o (10) wrench-x812 (101) 5,200 250 5% Rh/C (11) (CH3)XCl6-' si2 (103) 3, 450 250 KzPdCli (2.5) (CHIDxClh-xSlZ (108) 4,570 250 ti... [CnH5(CI I3)2P]zPdC/b (1.0) (CHshOl si 750 TABLE I Continued Pressure Sample 1 Catalyst type (g) Disilane (g.) (p.s.i.g.) Temp. C.) [(U4111031 aPdClz (CI-1010 04 12 (1 750 120 [(CiHo)aP z o z (1.0) CHOxCln-XSM (100) 3,725 120 [(C|H9)3P]2Pd0l (0.5) CHaClzSlSlClzCHa (50) 3,000 120 [(C4He)aP zPdCl1 (0.52) (CH3)2ClS1SiClzCH3 (52) 3,000 120 5% Pd/C (0.3) CBHE(CH3)2SXSKCHQ)2CAH5 (10) 55 25 5% Pd/C (0.1) CiHn(CHa)zS1Si(CI-Ia)2C4Hn (5) 55 25 5% Pd/C (0.3) (C a)z Si i(CHa)zH (7) 55 25 1s 5% Pd/C (0.3) (CHaOhSn (7) 55 25 i All these reactions were carried out in the presence of an inert solvent,

1 (CH3)xClfl-1Si2 refers to a mixture of the disilanes (CHmSizCh and either cyclohexane or 2,2,5-trimethylhexane. This solvent was used as a (CHQZSi CL standard for quantitative g.1.c. analyses of the reaction mixtures.

Products (weight percent) Sample CHaHzSlCl (CHmHSiCl CH3HS1C12 CH SlClI! (CH3)2S1C12 (C 3)xGifl-1Sii Others 1.1 12. 4 5. 3 1.0 81. 6 1. 5 6.5 4. 4 2.3 73.9 Unknown (11.7). 0. 5 3. 5 7.6 0.5 80.8 Unknown (71). 0.5 6.0 9. 6 1. 3 72.1 Unknown (10.5). 0.9 21, 2 22.0 11.3 22.8 Unknown (21.2). 0.1 43. 2 6. 7 0. 1 26.1 Unknown (23.9). 2. 4 48. 8 21.8 8. 7 12. 6 Unknown (3.5). 6 8 63.6 7. 9 3. 2 8.1 Unknown (10 4) HSiCl 69 24.4 3.5 29.8 2.0 8.9 Unknown(26). 2.8 39.7 28.3 6.5 11.2 Unknown(5.2). (0 93311 030);(CHa)eSi2(20)- CflH5(CH3)SiH CaH5(CH3) 2S1Si(CH )2CuH 17 "II l(O i)aSiO] I (OHQ)sio1l oH.).si. 25 18 (CH3O)3SiH(2O); (011.0 s1 5 (C a0)eSl2(75).

That which is claimed is: v metal catalyst (3) is palladium on charcoal. 1. A process for preparing hydrosilanes of the formula 3. The method as recited in claim 2 in which the disilane l) R SiH, comprising 40 is (CH Si A. contacting l. a disilane of the formula R SiSiR in which R is selected from the roup consisting of alk l radicals of from one to 51X car on atoms inclusive, al oxy radicals of from one to six carbon atoms inclusive, a phenyl radical, a halogen atom, a 3,3,3-trifluoropropyl radical, a hydrogen atom, and a trimethylsiloxy radical, with 2. hydrogen gas under pressure, and B. heating the above admixture at a temperature of from 25 C. to 250 C., in the presence of 3. at least 1.0 percent by weight based upon the weight of the disilane (l) of a transition metal catalyst, and thereafter C. recovering the hydrosilane. gifhe method as recited in claim 1 in which the transition 4. The method as recited in claim 2 in which the disilane l is C H (CH Si-Si (CH C H 5. The method as recited in claim 2 in which the disilane l is H(Cl-l SiSi(CH H.

6. The method as recited in claim 2 in which the disilane l is (CH O) Si 7. The method as recited in claim 1 in which the transition metal catalyst (3 is [(C H P] PdCl 8. The method as recited in claim 7 in which the disilane l) is a mixture of (Cl-l Si Cl and (CH Si Cl 9. The method as recited in claim 7 in which the disilane l) is CI Si- 10. The method as recited in claim 7 in which the disilane 

2. The method as recited in claim 1 in which the transition metal catalyst (3) is palladium on charcoal.
 2. hydrogen gas under pressure, and B. heating the above admixture at a temperature of from 25* C. to 250* C., in the presence of
 3. at least 1.0 percent by weight based upon the weight of the disilane (1) of a transition metal catalyst, and thereafter C. recovering the hydrosilane.
 3. The method as recited in claim 2 in which the disilane (1) is (CH3)6Si2.
 4. The method as recited in claim 2 in which the disilane (1) is C6H5(CH3)2Si- Si (CH3)2C6H5.
 5. The method as recited in claim 2 in which the disilane (1) is H(CH3)2Si- Si(CH3)2H.
 6. The method as recited in claim 2 in which the disilane (1) is (CH3O)6Si2.
 7. The method as recited in claim 1 in which the transition metal catalyst (3) is ((C4H9)3P)2PdCl2.
 8. The method as recited in claim 7 in which the disilane (1) is a mixture of (CH3)2Si2Cl4and (CH3)3Si2Cl3.
 9. The method as recited in claim 7 in which the disilane (1) is Cl6Si2.
 10. The method as recited in claim 7 in which the disilane (1) is Cl(CH3)2Si- Si(CH3)2Cl. 